Anthracnose is one of the most common and serious diseases affecting watermelon crops. It is prevalent in watermelon-growing regions across the country, particularly in the rainy southern areas, where it significantly impacts stable production, high yield, and fruit quality. The disease can occur at all growth stages, from seedlings to mature plants, and affects leaves, vines, and fruits.
In seedlings, the disease causes dark brown spots near the soil surface, leading to wilting and collapse. On the leaves, symptoms begin as small, yellow, water-soaked spots that gradually expand into brown lesions. A purple-black margin forms around the spot, with small black dots or pink, sticky masses appearing on the surface. As the lesions grow, they merge, causing the leaves to dry out and die. On petioles and vines, narrow brown depressions develop, which can lead to vine death if not controlled. If the fruit stalks are infected, young fruits become dark and shrivel, eventually dying.
On ripe fruits, the disease starts as a water-soaked ring, followed by a crater-like circular lesion. Multiple concentric rings appear, covered with pink, sticky spores. Severe infections cause deformation of the fruit, and the lesions may merge, leading to complete rotting of the watermelon.
To manage anthracnose effectively, several prevention and control measures should be taken:
1. **Use resistant varieties and treat seeds properly**. Selecting disease-resistant watermelon varieties is crucial. Some highly resistant varieties include Qingfa No.8, Humidity-proof 8802, Huami No.8, Qingnong No.5, Huami No.10, Zhengkang No.7, Extra-large Zhengkang No.3, Qingfa No.12, and Lubao Golden Flower King. Seed treatment before sowing is also important. Soaking seeds in 0.1% potassium permanganate for 5–6 hours or in 100 times diluted agricultural streptomycin for 10 minutes can help prevent infection. After soaking, rinse the seeds 3–4 times before sowing.
2. **Implement crop rotation and proper fertilization**. Rotate crops every 3–4 years in paddy fields and 5–6 years in dry land. Apply well-decomposed organic manure along with phosphorus and potassium fertilizers, while reducing nitrogen input to enhance plant resistance. Using deep trenches and mulching with sorghum film helps lower soil moisture and humidity, creating an environment less favorable for pathogen growth.
3. **Improve field management**. Prune and train vines regularly to maintain good air circulation and sunlight exposure. Avoid overwatering and ensure proper drainage to reduce disease spread.
4. **Apply chemical treatments when necessary**. Early application of fungicides is effective. Options include 70% thiophanate-methyl (600x), 15% pyrethroid (1000x), 20% carbendazim (3000x), 60% chlorothalonil (500x), or 80% anthrax oxime (800x). Alternatively, 70% mancozeb (500x) can be used. Spray every 7 days, applying 3–4 times, and alternate between different chemicals for better results.
By combining these strategies, farmers can significantly reduce the impact of anthracnose and ensure healthier, more productive watermelon crops.
Author unit: Vegetable Station of Malipo County Agriculture Bureau, Yunnan Province
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